1. Field of the Invention
The present invention relates to an airbag device for vehicle which develops and inflates an airbag for protecting an occupant.
2. Description of Related Art
In the prior art, Japanese Patent Laid-Open No. 2002-029361, especially in paragraph No. 0019 and FIG. 9, discloses an airbag device for front passenger's seat including a flow regulating cloth in an airbag body. When inflation gas flows in an airbag, in this airbag device, the flow regulating cloth helps inflate the airbag body while directing gas outward in left-right direction. Accordingly, the airbag body completes inflation while being developed widely in left-right direction, without unnecessarily protruding toward a passenger.
In conventional airbag devices for front passenger's seat, however, a flow regulating cloth has a band shape extending vertically, and its width is the same as transverse width of an opening of a case. The case is adapted to accommodate and hold a folded airbag and an inflator for supplying the airbags with gas. The flow regulating cloth is joined to upper and lower edges of an opening of the case at upper and lower ends of the band shape thereof.
This means that transverse dimension of the flow regulating cloth is short. Because of this, in an initial stage of inflation of the airbag body, the flow regulating cloth emits inflation gas into the airbag body before protruding from the case and completing inflation. In other words, this is not a gas flow into the airbag body in a state in which the flow regulating cloth is protruded from an instrument panel in front of front passenger's seat and is completely inflated. Accordingly, the flow regulating cloth cannot easily supply inflation gas outward in left-right direction, i.e., to the airbag body. In other words, even if the flow regulating cloth still in the case emits inflation gas to the airbag body, a portion of the airbag body protruded from instrument panel is not developed widely in left-right direction. Consequently, in conventional airbag devices for front passenger's seat, there is a room for improvement in suppressing partial protrusion of the airbag toward front passenger's seat in the initial stage of inflation.
In the prior art, moreover, Japanese Patent Laid-Open No. 5-042855 discloses an airbag device for vehicle which deploys an airbag for protecting an occupant. This airbag is provided with an auxiliary bag in an airbag body. This auxiliary bag inflates at first and redirects gas before supplying the same to the airbag body for promoting deployment of the airbag body. In this kind of airbag device, when fed with inflation gas, the auxiliary bag inflates firstly, and then the airbag body completes inflation with inflation gas flowing out of the auxiliary bag.
However, in the airbag device in the prior art, when the airbag is folded for accommodation in a housing, the airbag body and auxiliary bag are folded together from flattened multi-ply state.
With this construction, since the auxiliary bag cannot complete inflation and development before unfolding of the airbag body, the auxiliary bag does not deploy swiftly. As a result, in the airbag device in the prior art, there is a room for improvement in the auxiliary bag's redirecting and supplying a great deal of inflation gas in predetermined directions for promoting inflation of the airbag body.
As a countermeasure against this problem, it is conceivable to increase output of an inflator. However, employing a high-output inflator may increase internal pressure of an airbag in the initial stage of inflation, which is not suitable when the airbag is likely to engage an occupant in the initial stage of airbag inflation.